DESCRIPTION: The hypothesis to be tested is that exposure of mollusks to carcinogens in the environment, such as polycyclic aromatic hydrocarbons (PH), combined with tumor promoters (PCBs) causes p53 gene mutations and leads to leukemia. This hypothesis will be addressed as follows: 1) The applicant will extend analyses of p53 gene expression by comparing mollusks from sites with high and low contaminant levels. She will use reverse transcriptase/polymerase chain reaction-single strand conformation polymorphism (RT/PCR-SSCP) to evaluate p53 sequences and will address the hypothesis that p53 mutations occur in animals collected from PAH/PCB contaminated sites. 2) Normal clams will be exposed to PAH/PCB in a controlled laboratory environment to determine if mutant p53 is expressed and leukemia induced. Following in vitro fertilization, molluskan embryos will be exposed to PAH/PCB. The following determinations will be made: 1) The rate of embryogenesis following in vitro fertilization from the first polar body to metamorphosis (1.5 weeks post fertilization). 2) The pattern of wild type versus mutant p53 gene expression at precise stages during early embryonic development. 3) The induction of leukemia in young adults exposed during embryogenesis to PAH/Aroclor 1254.